Hey - I have a 2007 vw passat 2.0t with an AVIC Z1 (updated and hacked with 2012 maps, thanks Garrett!) and about two months ago a guy rear-ended me. Since then, and we're not entirely sure if it was already like that before the accident as it only rains in wintertime in the Bay Area... Right after we got it back, it started raining and we found out every time we turn on the rear wipers (whether by itself OR with the front wipers as well) the Z1 turns off, and only turns back on when the rear wipers are off (front can be on, the front doesn't affect it at all). Any ideas what's going on here and how to fix it?? 

Thanks in advance!

Sounds like you've got a short somewhere. Was any work at all done on the wiring for your rear wipers during the repair process from your accident? I imagine whoever did the repair screwed up the wiring somehow for the wipers. It's also possible they didn't check the wiring all the way through and a part of it got pinched between metal and is now grounded to the vehicle.

Nope. Only work done was new bumper, new exhaust. I'm thinking it's possible that the problem was there before the accident. There wasn't any damage to the rear door. I've checked the wiring inside that door (the car came with this system and a rear camera, the camera has never worked since I bought it) and it looks fine to me. Where else could the short be? (the Z1 DID pop out of the dash during that accident, and the mechanic put it back in)

Very odd... maybe the issue is at the headunit then? I'm honestly not sure. Might be easiest to have an audio shop go around with a meter and find the exact cause of the issue.